The present invention is directed to a multi-cell radio system for a communication system with exchange systems that have periphery assemblies and/or external radio exchange units for the connection of base stations. Each mobile terminal equipment is allocated to exactly one periphery assembly and/or radio exchange unit on the basis of an identification information specific to the terminal equipment. Radio connecting paths to or, respectively, from mobile terminal equipment can be produced such that, regardless of the location of the terminal equipment, they always ensue via the periphery assembly and/or radio exchange unit allocated to it.
In systems of this type, one or more base stations for mobile terminal equipment (cordless telephones) as well as, usually, for fixed terminal equipment are allocated to each exchange system.
The switching-oriented software that realizes the subscriber performance features usually runs in one or more central computer assemblies of the switching systems. The wire-bound terminal equipment are thereby connected via periphery assemblies with their own processor. The software of the periphery assemblies thereby does not realize and switching-oriented performance features of the system but is responsible for the hardware/software conversion, for example typically layer 1 and layer 2 according to the ISO OSI 7-layer model given digital interfaces.
Given carrier frequencies in the 900 Mhz or, respectively, 1.9 GHz range and standard, medically compatible transmission powers, the efficient region of a base station in buildings is limited to an ambience of approximately 20-50 m (see ETSI Standards CT 1, CT 2, DECT). This ambience that is supplied by a base station is called "cell". In practice, for example in a company building, this ambience or region does not meet the mobility demands, so that a switching system has a plurality of base stations.
There is a demand that each terminal equipment, both in its quiescent condition as well as in its activated call condition, can be arbitrarily moved between the radio cells of every switching exchange, as well as, within a network of switching exchanges. The mobility of the mobile terminal equipment in the quiescent condition is referred to as "roaming" in the technical jargon and the mobility in the activated call condition is referred to as "handover".
PCT reference WO 94/16531 discloses a system of the type wherein the control program in the radio exchange units sees to it that the telephone connections of a mobile terminal equipment ensue via the radio exchange unit allocated to the mobile terminal equipment regardless of its location. External radio exchange units are thereby employed. Another realization is disclosed by PCT/EP92/00418 reference, whereby a periphery assembly is employed as server instead of the external radio exchange units, this periphery assembly (just like the external radio exchange unit) simulating the connection of terminal equipment types known to the switching system via fixed connections (ports).
If the mobile terminal equipment participating in the telecommunication connections are to have the performance features allocated to them in their originating switching system available to them unrestricted and independently of location in the entire efficient region of all base stations, then the demand derives that a signaling connection between the "home" radio exchange unit and the terminal equipment must be set up and maintained in addition to the voice channel connection disclosed by PCT reference WO 94/16531.
It is thereby important that the signaling information of a mobile terminal equipment, for example dialed numbers, pressing the signal key, etc., always proceed into the "home" exchange system via the simulated "personal" port independently of the momentary location of the mobile terminal equipment. Only in this way is it assured that the mobile terminal equipment is supplied with its authorizations, for example direct access, personal, centrally stored abbreviated dialing destinations, etc., that is, with what is referred to as its "user profile".
Signaling information of a mobile terminal equipment that is relevant for the switching system must thereby be converted by the radio exchange unit into the protocol of the wire-bound terminal equipment type simulated in the direction of the switching system. An inverse conversion is analogously required for signaling information that derive from the switching system and that is intended for the mobile terminal equipment. Thus, during a call connection it is not only the voice data that must be constantly looped via the "visited" radio exchange unit through to the "home" radio exchange unit; rather, the same is also true of the signaling information between mobile terminal equipment and "home" radio exchange unit.